1. Field of the Invention
This invention relates generally to computer network gateways and more particularly to computer network gateways that connect a local area network to one or more distinct networks sharing the same electrically contiguous communication channel.
2. Description of the Related Art
The expansion of the Internet and the world wide web, the prevalence of telecommuting, and the anticipation of video on demand has generated a demand for the delivery of digital information to customer premises at bandwidths higher than can be delivered using traditional voice-grade modem technology.
Various solutions to the high bandwidth delivery problem are under development. Unfortunately, many of these solutions require the installation of a new wiring or cabling infrastructure to deliver information to a customer premises. One class of technology that does not have this drawback is digital subscriber line (xDSL) technology. Digital subscriber line technology has the advantage that it uses the existing subscriber line (local loop) infrastructure to deliver a higher bandwidth signal to a customer premises. This means that it uses the existing unshielded twisted pair (UTP) copper wiring that connects to a customer premises (subscriber premises).
The preferred xDSL technology, Asymmetric Digital Subscriber Line (ADSL), achieves the delivery of higher bandwidth by installing ADSL modems at both ends of the subscriber loop (e.g., at the telephone central office and at the customer premises). ADSL signals are then transmitted between the ADSL modem at the central office (ATU-C), and premises ADSL modem (ATU-R) over the existing UTP subscriber loop wiring.
FIG. 1 illustrates the spectral allocation 100 on an asymmetrical digital subscriber line (ADSL). The baseband portion of the spectrum is allocated for POTS connections 101 and the portion from 25 KHz to 1.1 Mhz is allocated for ADSL signals 102. ADSL signals 102 provide access to wide area computer networks and the POTS connections provide access to the public switched telephone network (PSTN).
Many customer premises provide xDSL access to more than one computer at a premises. Conventionally, this multiple access is provided using a 10baseT LAN to connect multiple computers to an xDSL modem/hub. The xDSL modem/hub performs xDSL modem functions and additionally may perform gateway (networking bridging) functions to facilitate communication between the premises LAN and the WAN made accessible via xDSL technology.
FIG. 2 illustrates a conventional xDSL system that provides multiple computers 201 with access to a wide area network (WAN) 202 via xDSL. The exemplary xDSL system uses asymmetrical digital subscriber loop (ADSL) technology. The system includes a conventional ADSL modem/hub 203 that operates as a network hub (e.g., a 10/100baseT Ethernet hub) for local area network 205. LAN 205, also known as the Premises Distribution Network is a point to point LAN having a star configuration centered around the hub portion of ADSL modem/hub 203. Installing LAN 105 involves the installation of a wiring network that supports 10/100baseT Ethernet. This means that new wiring or cabling must be xe2x80x9cpulledxe2x80x9d for each computer 201 to be included in LAN 205
ADSL modem/hub 203 is coupled to a telephone central office 207 via a subscriber loop. ADSL modem/hub 203 includes a POTS splitter 213 that may couple plain old telephone service signals to the exiting (installed) plain old telephone service (POTS) UTP wiring (POTS wiring) 206 at the customer premises 204.
In operation, a conventional ADSL modem 208 (ATU-C) located at central office 207 receives digital signals from a wide area network 202, modulates the received signals and then places them on the UTP subscriber loop using a POTS splitter at the central office. This POTS splitter combines ADSL signals and POTS signals for transmission to the premises and conversely splits POTS and ADSL signals upon reception from the premises.
Preferably, ADSL modem/hub 203 is located at the telephone Network Interface (TNI) 210 at the demarcation point between the subscriber loop and the customer premises so that the output of the POTS splitter 213 is coupled to the premises UTP wiring before any branching occurs and before the installation of any RJ-11 jacks. The subscriber loop is thus terminated at the ADSL modem/hub, which is an active device requiring AC power. Locating POTS splitter 213 elsewhere at a customer premises requires knowledge of the customer premises wiring topology and the willingness to electrically xe2x80x9cbreakxe2x80x9d the wiring at the splitter insertion point in order to insert the active device (e.g., the ADSL modem/hub 203). Without a clear understanding of the customer premises wiring topology, it is difficult to know which part of the premises wiring will carry both ADSL and POTS signals as opposed to only POTS signals. Most typically, the POTS splitter is integral with the ADSL modem/hub (as shown in FIG. 1) therefor, it is preferred to install the ADSL modem/hub 203 at or near the TNI 210. Placing on ADSL modem/hub 203 at the TNI 210, however, has certain drawbacks such as the need for an AC power source/outlet near the TNI and the risk of exposure to harsh environmental elements (e.g., temperature extremes, rain, etc.). Further, when the hub and the modem are combined, new wiring must be xe2x80x9cpulledxe2x80x9d to the TNI from computers 201 to complete network connections.
The above described system known in the art provides for communication between multiple device networks: a WAN, a LAN at a customer premises and the PSTN. This communication is enabled using an active device (e.g., an ADSL modem/hub) that breaks the electrical continuity between the subscriber loop and the premises LAN (Premises Distribution Network) with the installation of an active device, typically a hub, in order to provide hub/gateway functionality between the LAN and the WAN.
The above described system has several drawbacks. The system requires the installation of a new active device (the hub 203) that adds considerable cost and installation complexity. Further, installing new wiring for a LAN at the customer premises is complex and costly, and the LAN and the subscriber loop do not share the same electrically contiguous communications medium. The LAN wiring does not support DC current flow from the subscriber loop, which means POTS, and more particularly, POTS lifeline service, is not supported on the LAN wiring.
Thus, there is a need for an improved system and method for interconnecting distinct premises LAN and subscriber loop WAN device networks without the need for insertion of an active hub/gateway device between the premises POTS wiring and the subscriber loop, without the pulling of new cable to implement the premises LAN, and without breaking the electrical continuity (DC current capability) of the wiringxe2x80x94which would preclude POTS lifeline service.
In accordance with the present invention, there is provided a system and method for providing bi-directional communication between a first device network and a second device network using a shared electrically contiguous communication channel such as an existing (already installed) customer premises plain old telephone (POTS) wiring. Each device network is coupled to the shared electrically contiguous communication channel and each are further allocated separate spectral bands for use on the shared communication channel. Thus, two distinct device networks coexist on a single shared communication channel using frequency division multiplexing. Communication between the distinct device networks is perfected by converting signals from the spectral band associated with the source network to the spectral band(s) associated with the destination network.
The gateway server of the present invention is advantageously operatively coupled to the shared communication channel without breaking the electrical continuity of the shared communication channel. Because electrical continuity is not broken, DC current may pass; and the customer premises wiring is capable of maintaining POTS lifeline services and POTS signaling protocols.
In a centralized architecture, the virtual gateway of the present invention includes first and second modems, each associated with one of the device networks. It should be understood that as used herein, xe2x80x9cmodemxe2x80x9d means a modulator-demodulator device or a transceiver and the like. Further, as used herein xe2x80x9cmodemxe2x80x9d includes modems that effect direct current (DC) baseband signaling as well as bandpass and highpass signaling and the like. The modem associated with the first device network has a receive portion and a transmit portion for converting signals from the spectral band associated with the first network to baseband and for converting baseband signals to the spectral band associated with the first network, respectively. Similarly, the modem associated with the second device network has a receive portion and a transmit portion for converting signals from the spectral band associated with the second network to baseband and for converting baseband signals to the spectral band associated with the second network, respectively. The virtual gateway server additionally provides for communication of baseband data between the first and second modems using means conventionally found within a personal computer or similar computing device (such as a PCI bus, etc.). It should be understood that as used herein xe2x80x9cbasebandxe2x80x9d includes data not modulated by a carrier frequency, such as data processed by a microprocessor of transferred over a personal computer bus such as a PCI bus.
Information is sent from a sending network to a receiving network by first demodulating the information in accordance with the protocol and modulation scheme associated with the sending network to generate baseband data. The baseband data is then processed to generate a band pass signal in accordance with the modulation scheme and protocol associated with the receiving network. The baseband processing includes any required protocol conversion to translate the data from the protocol associated with the sending network to the protocol associated with the receiving network.
In accordance with another aspect of the invention, rather than locating the first and second modems centrally on a gateway server, the gateway functionality is distributed across a plurality of network clients. Thus, first and second modems, each associated with the first and second networks, respectively, are located at a plurality of network clients. Advantageously, this distribution of the gateway functionality reduces network traffic and improves overall system performance because the same data need not be transmitted on multiple spectral bands in order to be received by clients of either device network.
In accordance with another aspect of the invention, the virtual gateway functionality is partially distributed such that the modems located at the clients provide both transmit and receive capability in the spectral band associated with the first network but provide only receive capability in the spectral band associated with the second network. The transmit capability associated with the second network is not distributed but instead is centrally located at a server. This partially distributed architecture is particularly advantageous when the second network is characterized by asymmetrical data traffic patterns. For example, in cases where the second network is a wide area network supplying video on demand, the data traffic is highly asymmetrical. Advantageously, this partial distribution of the gateway functionality reduces network traffic and improves overall system performance because data transmitted on the second network need not be retransmitted in the spectral band of the first network to be received by clients of the first network.
The features and advantages described in the specification are not all-inclusive, and particularly, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings, specification, and claims hereof. Moreover, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and may not have been selected to delineate or circumscribe the inventive subject matter, resort to the claims being necessary to determine such inventive subject matter.